If you are ever in the area, Portsmouth dockyards are well worth a visit.
Not just those gates, but also:-
H.M.S. Victory; The Mary Rose; a recently restored WW1 'patrol boat; H.M.S. Warrior
(this one scared the French as it was the first British warship to have washing machines!);
several museums (both in the docks & within a few miles) Gift shops & eateries,
then a short boat/taxi ride to Gosport will get you to the Submarine museum.
The last time I went they pointed out to me that the ticket is valid for a year, so you
can go back.